Evaluation of Distal Upper Extremity Musculoskeletal Load During Routine Colonoscopy

Abstract

Background: Physicians who perform endoscopies are at increased risk for developing recurrent thumb, hand, elbow and low back pain. Musculoskeletal disorders of the upper extremities are related to repeated, forceful movements of the hands and arms. As the demand for colonoscopy increases, so will the physical loads on the hands and arms of endoscopists. The risk factors of upper extremity overuse injuries during routine endoscopy, such as applied pinch force and muscle loads, have not been evaluated during routine endoscopy. We performed a pilot study to determine right thumb pinch force and hand and wrist muscle activities during colonoscopy. Methods: Three gastroenterologists were studied while each performed three colonoscopies. Electromyographic (EMG) activity of the right and left forearm extensor carpi radialis (ECR), right and left flexor digitorum superficialis (FDR), and left abductor pollicis longus (APL) was measured with surface electrodes. Summary measures of EMG data were calculated using the amplitude probability distribution function (APDF), which is a method to quantify muscular activity by normalizing it to maximum voluntary contraction (MVC). Prior studies have shown median levels of muscle activity (APDF 50%tile) of >7-20% MVC and low levels of muscle activity (APDF 10%ile) of >2-5% MVC are associated with increased risk of injury. Right thumb pinch force was measured using a thin profile, custom designed pressure sensor. Prior studies have shown peak pinch force levels (APDF 90%tile) of >10N are associated with an increased risk of injury. Results: The mean peak pinch force across the 9 patients (APDF 90) was 8.6N (SD ± 2.1). The highest pinch forces occurred during insertion: APDF 90 = 10.4N in the left colon and APDF 90 = 10.1N in the right colon. The highest muscle activities were observed in the left ECR (APDF 10 = 10% MVC and APDF 50 = 20% MVC). Left ECR activity was greatest during insertion into the left colon (APDF 10 = 9.0%, APDF 50 = 25.1%) and right colon (APDF 10 = 11.4%, APDF 50 = 23.9%). APDF 10 values of the other muscle groups studied did not exceed 5% of MVC, and APDF 50 values did not exceed 20% of MVC. Conclusions: Based on this pilot data, colonoscopy is associated with a borderline risk of musculoskeletal disorders of the upper extremities, specifically right thumb and left wrist extensor injury. Repeated, high thumb pinch forces can lead to DeQuervain's tendinitis and carpal tunnel syndrome. Repeated, high left ECR muscle loads can lead to second and third extensor compartment tenosynovitis at the wrist and epicondylitis. Further study is needed to identify modifiable risk factors and evaluate methods to reduce this risk.